1. Field of the Invention
The present invention relates to an infusion portal on the side of an infusion sleeve of a surgical instrument.
2. Discussion of Related Art
Phacoemulsification instruments and irrigation/aspiration instruments are known that have infusion portals in their malleable infusion sleeves. Alcon Surgical Laboratories commercializes such a phacoemulsification system under the name SERIES 20000® LEGACY®. The phacoemulsification system is commercialized with a handpiece and malleable infusion sleeves with infusion portals. The sleeves partially shroud needles, such as those commercialized under the tradename Mackool System® such as the MACKOOL MICROTIP or the MACKOOL FLARED ABS, which are named after the present inventor.
The infusion portal in the malleable infusion sleeve is typically formed by punching out that portion of the sleeve that is to form the infusion portal, thereby leaving a hole or orifice. Conventionally, the wall of the infusion port is at a 90° angle to the entry of the hole or orifice.
The present inventor, who has performed thousands of cataract operations, has made some observations. When inserting the needle and sleeve through an incision, the edges of the portal tend to become caught on the edges of the adjacent incision. This requires the surgeon to press more forcefully in an attempt to insert the needle and sleeve to a desired location. Trauma to the surrounding tissues may result as a result of trying to break the portal free of being caught on the edges of the adjacent incision.
Indeed, by twisting and turning the handpiece (basically oscillating it as it is advanced), the tip can eventually be introduced. Greater effort is required and some surgeons (fearful that the manipulation causes trauma) simply make the incision larger than optimum so that tip insertion is easier. A larger than necessary incision results in fluid leakage from the eye during the procedure, with resultant greater difficulty in controlling eye pressure during the surgery, potential collapse of the eye with trauma to ocular structures such as the cornea, iris, posterior lens capsule, etc. In addition, a larger incision results in greater total fluid flow through the eye, and this fact alone cause greater trauma.
On the other hand, pushing and oscillating the instrument through a tight incision can cause the edge of the portals to damage the cornea, particularly the inner lining of the cornea known as Descemet's membrane and the attached corneal endothelial cells, which can be stripped from the portion of the cornea above them (the corneal stroma) to which Descemet's membrane is normally attached. This is an extremely serious complication, well-known to occur as a result of the insertion of blunt instruments through corneal incisions, and this may so seriously damage the cornea that a corneal transplant may become necessary to restore sight. I have personally seen this occur as a result of sharp edged portals on several occasions.
No matter how skillful the surgeon, the current design requires greater force in order to accomplish insertion unless the incision is made larger than would otherwise be necessary to permit insertion of the tip or the portals are made smaller than optimally desirable. If the latter is done, the portals may be placed more toward the tip of the tapered infusion sleeve, where its diameter is less. Thus the portal may avoid contact with the sides of the incision during insertion.
However, smaller than optimal portals restrict the rate at which fluid can enter the eye, thereby limiting the rate at which the pump can run as it removes the cataract (i.e. a lower aspiration flow rate must be used), as well as limiting the suction level that can be applied to the cataract to remove it. Using less suction/vacuum generally results in a less efficient and slower procedure, and also requires that more ultrasonic energy be used to remove the cataract. It is therefore desirable to have little or no fluid leakage from the incision during the period when the tip is in the eye, and to construct the infusion sleeve with portals large enough so that they do not create any limitation to infusion flow into the eye.